1. Field of the Invention
This invention relates to cannulas and, more particularly, to a cannula which is oval-shaped in cross-section and therefore ideally suited for use in minimally invasive surgical procedures.
2. Description of the Related Art
Cannulas have a wide variety of applications during surgical procedures. For example, in coronary surgery, venous and arterial cannulas are used to conduct blood between the body and bypass equipment. Cannulas are used to conduct cardioplegia solution for both antigrade and retrograde solution administration, and cannulas are also used as vents, sumps, and for chest tube fluid suction. The structure for these known cannulas generally comprises a cannula body which is circular in cross-section and has at least one lumen extending therethrough which is similarly circular in cross-section. Examples of these structures are seen in U.S. Pat. Nos. 4,639,252, 4,129,129 and 5,395,330.
A recent trend in surgical procedures is to minimize the size of the access apertures formed in the chest cavity. These procedures include mini-sternotomy and minimally invasive cardiac surgery. In each of these procedures, the goal is to reduce the size of the aperture in the chest wall. One problem in achieving this goal is the size, geometry, and space requirements for the instruments, cannulas, and the like which must pass through the reduced size apertures.
The cannula according to the invention overcomes the problems of the prior art by providing a cannula having a prescribed geometry, which more efficiently occupies the space of the aperture without adversely affecting the fluid rate therethrough, and an obturator for use with the cannula.
In accordance with one embodiment of the invention, an obturator for a cannula is provided. The cannula has proximal and distal ends, and a lumen extending therebetween. The distal end of the cannula is circular in cross-section. The cannula further includes a first portion having a non-circular cross-section and at least one fluid aperture formed adjacent the distal end. The obturator includes an elongate member and a flexible disc which is coupled to a distal end of the elongate member. The elongate member and flexible disc of the obturator are adapted to be telescopically received in the lumen of the cannula, and the flexible disc is configured to restrict the flow of fluid, entering the at least one fluid aperture, through the lumen.
In another embodiment of the invention, a cannula assembly includes a cannula and an obturator. The cannula has proximal and distal ends, a lumen, a first portion, and at least one fluid aperture as described above. The obturator, which is telescopically received in the cannula lumen, includes an elongate member and a flexible disc. The flexible disc substantially restricts the flow of fluid, entering the at least one fluid aperture, through the lumen, when the obturator is fully inserted in the cannula.
The invention is also directed to a method of positioning a fluid conducting cannula in a body. The method includes the steps of providing a cannula, such as that described above, and inserting an obturator in the lumen of the cannula. The obturator includes an elongate member and a flexible disc coupled to a distal end of the elongate member. The flexible disc substantially restricts the flow of fluid, entering the at least one fluid aperture, through the lumen of the cannula. The method further includes the steps of providing a percutaneous aperture in a body, inserting the distal end of the cannula in the percutaneous aperture, and positioning the cannula so that the first portion thereof extends through the percutaneous aperture.
The invention is further directed to a method of positioning a fluid conducting cannula in a body, including the step of providing a pre-assembled cannula assembly. The pre-assembled cannula assembly has includes a cannula, as described above, and an obturator disposed in the lumen of the cannula. The method further includes the steps of providing a percutaneous aperture in a body, inserting the distal end of the pre-assembled cannula assembly into the body through the percutaneous aperture, and positioning the cannula so that the first portion extends through the percutaneous aperture.
Other advantages of the invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific embodiments are given by way of illustration only, since, from this detailed description, various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.